How does geography play a role in Mexico City’s air pollution problem? A.
It is one of the world’s most populated cities.

B.
The number of cars has increased in the last ten years.

C.
The passing of NAFTA has allowed for more factories to be built in Mexico.

D.
It lies in a valley, surrounded by mountains, that traps in air pollutants over the city.

D. it lies in a valley, surrounded by mountains, that traps in air pollutants over the city.

Explanation: Being in a valley results in air pollution being contained to an area.

the perimeter of a triangle is 69 cm. side a is 5 cm shorter than side b. side c is twice as long as side a. find the length of each side. i need to know how to do it in 2 equations.  

equations:

a = b-5

c = 2a

a + b + c = 69